He misses his thumbs. That's the worst part about this entire situation. Hiccup is capable of making extraordinary inventions, create precise instruments and form-fitting saddles. He's not yet a master of smithing, but soon enough he will be.
But in order to smith, you need thumbs. It also helps to be human, instead of a temporary dragon.
Hiccup knows it's temporary, because he and Toothless have switched around three times already, each switch lasting a week, but it's getting shorter according to his calculations. Which are currently scratched into the sand in an imprecise manner, because he has to use his mouth and a long twig and Toothless loves getting his hands on a far smaller twig and create small drawings in between the large numbers.
“Down to six days, huh,” Astrid remarks. “How long before you and Toothless are basically the same?”
Numbers are not her strong suit, so Hiccup sits on his haunches as he does mental math and comes up with the answer.
The stick he picks up has been stripped of its bark by now, leaving the foul taste of dead tree on his teeth but Hiccup has little choice.
By then they'll switch every quarter day, so at most they have forty-five days to track down the völur who lay the curse on man and dragon. He still has no idea why the woman practicing her magic, her seidr, chose to curse them in the first place – he and Toothless had done nothing wrong! They had just been flying, further out than ever before. And a week later, when Hiccup woke, he was Toothless.
That had been a fun discovery.